A wind turbine blade having a longitudinal axis is provided. The wind turbine blade includes a root portion and a tip portion. The root portion has a supported end and an unsupported end. The tip portion is configured to be slidably received within the unsupported end of the root portion. A transverse gap is defined between the root portion and the tip portion. A transition element is affixed to the unsupported end of the root portion such that the transition element at least partially bridges the transverse gap. The wind turbine blade may further include blade cleaning elements and/or sensing elements, particularly in the vicinity of the transition element.
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9. A wind turbine blade comprising:
a first blade element;
a second blade element; and
a blade cleaning element attached to the first blade element and configured to remove unwanted material from a surface of the second blade element.
1. A wind turbine blade having a longitudinal axis, the wind turbine blade comprising:
a first blade element having a supported end, an unsupported end, a leading edge longitudinally extending therebetween, and an outer surface;
a second blade element having an outer surface and configured to be slidably received within the unsupported end of the first blade element; and
a transition element extending from the unsupported end of the first blade element, wherein the transition element has a longitudinally extending leading edge that is angled relative to the longitudinally extending leading edge of the first blade element.
15. A wind turbine blade defining a longitudinal axis, the wind turbine blade comprising:
a first blade element having a supported end, an unsupported end and a leading edge longitudinally extending therebetween;
a second blade element, wherein the second blade element is configured to slide, substantially longitudinally, into the first blade element;
a transition element extending from the unsupported end of the first blade element and having a longitudinally extending leading edge that is angled relative to the longitudinally extending leading edge of the first blade element; and
a sensing element having at least one component located within the transition element.
2. The blade of
3. The blade of
4. The blade of
5. The blade of
6. The blade of
a blade cleaning element, wherein at least a component of the blade cleaning element is attached to the transition element.
7. The blade of
a sensing element located in a region of the wind turbine blade where the first and the second blade elements slide past one another.
8. The blade of
a sensing element, wherein at least a component of the sensing element is attached to the transition element.
10. The blade of
11. The blade of
12. The blade of
13. The blade of
16. The blade of
17. The blade of
18. The blade of
21. The blade of
22. The blade of
23. The blade of
24. The blade of
25. The blade of
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The invention relates to a variable length wind turbine blade. Specifically, the invention relates to a variable length wind turbine blade having transition area elements.
Wind turbines create power proportional to the swept area of their blades. Increasing the length of a wind turbine's blades increases the swept area, which produces more power. A wind turbine's generator, gears, bearings, and support structure must be designed around the expected wind load and power production. At low wind speeds very long blades are desirable to get as much power as possible out of the available wind. At high wind speeds a wind turbine must control the power production and the mechanical loads developed. Eventually, if the wind speed becomes high enough, the turbine must shut down to avoid damaging components, so short blades are desirable to keep the turbine producing power in high winds.
The choice of a rotor diameter for a wind turbine is a design trade-off between energy production in low winds and load limitation in high winds. Wind turbine manufacturers often sell a variety of rotor sizes for a given wind turbine model. The rotor sizes are optimized for sites that have a low, medium, or high annual average wind speed. However, the rotor size selected is always a compromise, and there are conditions in which the turbine does not perform optimally because the rotor is too big or too small.
Disclosed in U.S. Pat. No. 6,902,370 issued Jun. 7, 2005 to Dawson, et al., entitled “Telescoping Wind Turbine Blade,” and incorporated by reference herein in its entirety, is a variable length wind turbine blade that allows for a large diameter in low winds and a small diameter in high winds. This is accomplished by having a root portion and a tip portion of the blades. The tip portion may be extended or retracted relative to the root portion, depending on the amount of wind present.
A sharp transition between the tip portion and the root portion reduces aerodynamic efficiency and generates aerodynamic noise. Thus, it would be desirable to provide a smooth transition between the two blade portions.
Wind turbines, especially when using retractable blade technology, require significant amounts of monitoring and controlling. For example, the extension and retraction of the tip portions of the blades must be monitored and closely controlled to ensure that all the blades extend and retract at the same time so as to prevent an unbalanced rotor. Thus, it would be advantageous to have a method of measuring the position of the tip portion of a blade. It would also be useful to sense other parameters that provide information about the operating conditions of the blades and wind turbine.
Because of the dust and debris in the wind, turbine blades often need cleaning. In the winter, blades have a tendency to get ice build-up. Especially in the case of a variable length blade, de-icing is important because the tip portion of the blade must retract into the root portion. Thus, it would be advantageous to have a method of cleaning and de-icing blades on a variable length wind turbine.
In one aspect, a wind turbine blade having a longitudinal axis is provided. The wind turbine blade includes a first blade element, a second blade element and a transition element. The first blade element has a supported end, an unsupported end, and an outer surface. The second blade element has an outer surface and is configured to be slidably received within the unsupported end of the first blade element. A transverse gap is defined between the outer surfaces of the first and second blade elements. The transition element may be affixed to the unsupported end of the first blade element. The transition element may at least partially bridge the transverse gap.
The wind turbine blade may further include a blade cleaning element, such as a wiping element, a de-icer, and an applicator. The blade cleaning element may be attached to one or more of the first blade element and the transition element. The blade cleaning element may be configured to remove unwanted material from the surface of the second blade element.
The wind turbine blade may include a sensing element. The sensing element may be attached to one or more of the first blade element, the second blade element and the transition element. The sensing element may be located in a region of the wind turbine blade where the first and second blade elements slide past one another.
In another aspect, a wind turbine blade includes a first elongated blade element and a second elongated blade element. The first elongated blade element has a leading edge extending from a supported end to an unsupported end. The leading edge is substantially linear over a majority portion of the first blade element. The second elongated blade element is slidably received into the unsupported end of the first elongated blade element. The first elongated blade element includes a transition element adjacent its unsupported end. The transition element has a leading edge that may not be aligned with the leading edge of the majority portion.
Features and advantages according to embodiments as disclosed herein will be apparent from the following Detailed Description taken in conjunction with the accompanying drawings, in which:
Varying the length of a variable-length wind turbine blade changes the rotor's swept area, thereby allowing one to regulate the amount of power generated from the wind. In low wind conditions, the blade length is extended to provide a rotor with maximum swept area so that a maximum amount of power can be extracted from the wind. In high wind conditions, the blade is retracted to reduce aerodynamic loading and to keep structural loads within the design criteria.
The variable-length blade of the present disclosure includes at least a first blade element and a second blade element. The first blade element may be a root portion having a supported end that is attached to the rotor hub and having an unsupported end positioned radially outward from the supported end. The first blade element includes a cavity that provides a housing for a drive mechanism for the second blade element. The second blade element may be a tip portion having a supported end located within the cavity of the first blade element and attached to the drive mechanism and having an unsupported end located radially outward from the supported end.
The second blade element is longitudinally moveable relative to the first blade element. As the second blade element is moved longitudinally, i.e., radially inward or outward as defined by the swept area, the effective length of the blade is varied.
In these variable-length, multi-element blades, a transition region is defined where the second blade element retracts into the first blade element. This transition region provides many opportunities not found on single-element blades. For example, the transition region may be ideal for a variety of sensors and/or indicators used to collect data useful for the operation of a wind turbine. The transition region may also be ideal for the placement of cleaning devices such as de-icers to maintain clean and ice-free blades.
Referring to
Referring back to
Root portion 16 is a generally elongated blade element extending from a first end 20 to a second end 22. The first, supported, end 20 is configured for attachment to hub 12. A metal fitting, such as a bolt flange 14 or studs, may be attached to first supported end 20 to assist in the attachment of root portion 16 to hub 12. The second, unsupported, end 22 has an opening 24 configured to receive tip portion 18.
Tip portion 18 is also a generally elongated blade element extending from a first end 26 to a second end 28. In this embodiment, the first end 26 is a supported end and the second end 28 is an unsupported end. Tip portion 18 may be hollow or solid.
Tip portion 18 is configured to longitudinally extend from (see
As best seen in
As best seen in
In FIGS. 3 and 5A-5C, a transition element 40 is shown affixed to root portion 16. As shown in
Transition element 40 at least partially bridges transverse gap 32. In some embodiments, transition element 40 may completely bridge gap 32, such that transition element 40 contacts outer surface 38 of tip portion 18. Further, in certain embodiments and as shown in
Transition element 40 may completely encircle tip portion 18, as shown in
Transition element 40 may be formed of rigid or flexible materials or a combination thereof. Thus, by way of non-limiting example, transition element 40 may be formed of the same material that is used to form root portion 16. Further, transition element 40 may be formed, at least partially, of a material capable of elastically deforming such that any change in the cross-section and/or position of tip portion 18, as it moves relative to root portion 16, may be accommodated.
Thus, in certain embodiments, as shown in
One or more blade cleaning elements 50 may be attached to transition element 40. For example, as best shown in
Multi-element wind turbine blades provide a unique opportunity to measure stress, flexure, relative position, load and other blade properties. By way of non-limiting examples, and as shown in
Sensing elements 60 may sense or provide information (i.e., data) for various different properties. For example sensing element 60 may sense displacement, velocity and/or acceleration of the blade portions. Sensing elements may further be used to sense or provide information on relative blade displacements, velocities and/or accelerations, i.e. measuring the movement of tip portion 18 relative to root portion 16. The sensed displacements, velocities or accelerations may be linear (e.g., substantially longitudinal or transverse) and/or angular (e.g., rotational around the longitudinal axis, pivotal in the plane of the swept area, or pivotal out of the plane of the swept area). In other embodiments, sensing element 60 may be used to sense a pressure or a load applied to a blade portion. The pressure or loads may be due to wind pressure or to one blade portion contacting another. In even another embodiment, sensing element 60 may sense a stress or strain within an element or a blade portion. Further, environmental data may be sensed by the sensing element(s) 60, including temperature, humidity, wind speed, air flow pressures, etc.
In certain embodiments, a single sensing element 60 may supply several pieces of information. For example, an accelerometer may measure acceleration, which may then be used to determine velocities and displacements. The sensed data may be collected during steady state and/or during transitional operation of the wind turbine. Further, the sensed data may be used for real-time control of the wind turbine or to collect data for future design purposes.
As shown in
In the embodiment shown in
In the embodiment of
In certain embodiments, sensing element 60 may also function as a safety element, providing information to a control system when travel, load, strain, temperature, etc. limits have been reached. In even other embodiments, sensing element may also function as a switch, not only sensing information, but also triggering an event. Thus, by way of non-limiting example, sensing element may include a first component in the form of an actuator and a second component in the form of a trigger, such that when the actuator contacts the trigger, a signal is sent to the control system to take a specific action. The actuator may, for example, be a protrusion extending from transition element 40, root portion 16 or tip portion 18 and the trigger may be a trip or break-away wire.
Materials used to make wind turbine blades, such as fiberglass, typically lend themselves to embedding other materials or sensors within the matrix of the blade. Thus, sensing elements or components of sensing elements may be embedded in the walls of the root or tip portions 16, 18. For example, switch 64 may be mounted on the root portion 16 and magnetic targets 65a, 65b may be embedded in wall of tip portion 18. Alternatively (not shown), switch 64 may be embedded in tip portion 18 and magnetic targets 65a, 65b may be mounted to a surface of, or embedded in, root portion 16. Other items, such as strain gauges, reflectors, etc. may be embedded to protect the sensing component or to provide a surface free of protrusions or attachments.
A person of ordinary skill in the art, given the benefit of this disclosure, would recognize that many other sensors may be placed in the transition region, including, without limitation, micrometers, potentiometers, accelerometers, strain gauges, dial indicators, angle indicators, linear movement indicators, encoders, optical devices, laser devices, ultrasonic devices, pressure bulbs, etc. Other conceivable possibilities for sensing information include an air bleeder port, limit switches, inductive switches, camera/logical comparisons, rheostats, piezoelectric technology, capacitance, infrared sensors, microwave, or fiber optic technology. Information received from sensing element 60 may be used as input for the control of wind turbine 2 and/or may provide valuable insight into the operating conditions.
Thus, for example, referring to
In another embodiment, as shown in
Transition element 40d may extend completely around tip portion 18 or only partially (as shown in
The present invention has been described in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure. Thus, for example, blade 10 may be composed of more than two blade elements. As another example, the unsupported end of the root portion may be slidably received by the unsupported end of the tip portion, i.e., the tip portion may slide over the root portion. Further, certain elements shown as mounted on root portion 16 and/or tip portion 18 may be mounted on transition element 40, or vice versa, as part of certain design variations. Even further, suitable mounting configurations and methods, such as whether the elements are mounted on outer or inner surfaces, or are removably or permanently attached, would be apparent to persons of ordinary skill in the art, given the benefit of this disclosure. All examples, whether preceded by “for example,” “such as,” “including,” or other itemizing terms or followed by “etc.,” are meant to be non-limiting examples, unless otherwise stated or obvious from the context of the specification.
Wallace, Jack, Dawson, Mark H.
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Apr 07 2009 | DAWSON, MARK H | Frontier Wind, LLC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 022537 | /0981 | |
Apr 10 2009 | WALLACE, JACK | Frontier Wind, LLC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 022537 | /0981 | |
Apr 13 2009 | Frontier Wind, LLC | (assignment on the face of the patent) | / |
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